Germany received a tip-off from a Palestinian informant in Beirut that Palestinians were planning an "incident", three weeks before the 1972 Olympic Games Munich massacre, a German news magazine has disclosed.

In a story published on Monday, Der Spiegel revealed that the tip-off, originally given to the Foreign Ministry in Bonn via the German Embassy in Beirut, was taken seriously enough to be passed onto the secret service in Munich, who were urged that "all possible security measures" be taken.

However, the Munich authorities failed to act in response, and have never acknowledged the tip-off in the last 40 years.

The terror attack, carried out by Palestinian Black September terrorists, resulted in the deaths of 11 members of the Israeli Olympic team.

Der Spiegel declared: "The federal government [in Bonn] and the local government of the state of Bavaria committed grave errors in their handling of the attack on Israeli athletes during the Olympic Games in Munich, and have kept the true extent of the failure under wraps until today."

The revelation comes after an initial 20 years following the event, in which the German authorities rebuffed any attempts to release information. This changed when Ankie Spitzer, widow of murdered fencer Andrei Spitzer, appealed on television in 1992 for information that would help explain how her husband died.

Following her appeal, Spitzer received a call from an anonymous government official and two weeks later, 80 pages of original documents turned up at the desk of Pinchas Zeltzer, the lawyer representing the victims' families. Yet the Bavarian Justice Minister denied the existence of official government archives.

Later that year, the archives were found and in 1994, the families filed suit against the federal government, the Bavarian government and the city of Munich. In an out of court settlement the families were awarded compensation of three million euros.

The Der Spiegl report also criticises the security measures taken by the German authorities in dealing with the "badly prepared" Black September group and the negligence shown by the Munich police chiefs at the time.